This invention relates to the electrostatic measurement art, and more particularly to a new and improved method and apparatus for determining the physical uniformity of a surface capable of being electrically charged.
One area of use of the present invention is in determining the surface quality and uniformity of photoconductive drums used in photocopiers, although the principles of the present invention can be variously applied to inspecting any surface capable of holding electrical charge. Heretofore, photoconducting drums have been inspected visually or by light scattering techniques to determine the presence of surface defects such as holes. These methods, however, are indirect in that they provide no measure of charge properties of the drum surface and they provide information only about the reflective properties of the surface.
It would, therefore, be highly desirable to provide a method and apparatus for quickly and reliably determining the physical quality and uniformity of a charged surface in a manner providing a measure of the charge properties of the surface. In providing such method and apparatus, important considerations involve minimizing electrical noise and maximizing resolution of detected signals. It would also be highly desirable to provide in such method and apparatus the capability of determining the size, number, and location of surface defects.